Speaker diaphragms are generally desired to have various characteristics, such as reduced high frequency distortion and reduced sound distortion. Such characteristics are mostly based upon physical properties (e.g. specific modulus, internal loss etc.) inherent to materials constituting the speaker diaphragms.
The speaker diaphragms are generally produced from paper, olefin resin, carbon fiber-reinforced epoxy resin, polyester and the like. Since paper has good physical properties in elasticity and internal loss, it is most commonly used for the speaker diaphragms. Paper, however, is susceptible when exposed to the external atmosphere, for example water, direct sun-light and ultraviolet rays.
A speaker diaphragm produced from olefin resin has higher internal loss than that of paper, and has flat frequency characteristics and reduced sound distortion. It, however, has low specific modulus and large sound distortion at a high frequency range.
A speaker diaphragm produced from carbon fiber-reinforced epoxy resin or polyester has a higher specific modulus than that of paper and has low sound distortion at a high frequency. It also has excellent heat resistance and weather resistance. The diaphragm is equal to paper in internal loss and therefore is not perfect.